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USM-0007
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Issue: B
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 2 of 47
Document Control
Issue
Date
Section
Description of Change
Reason for Change
14/02/2011
All Sections
First Draft
N/A
Section 8.2
Update to connector part
number
for
Array
connector on EPS
Incorrect part number
specified in Rev A of
document.
Table 11-3
Update to
equations
telemetries
Rev B of this document
reflects current build level of
product (Rev C)
Product
Part Number
Revisions covered
Notes
Cubesat 3U Electronic Power
System
25-00221
C
2x16V/8W, 5V/3W BCR
A
B
25/09/2014
theoretical
for
all
Revision Control
Acronyms and Abbreviations
BCR
Battery Charge Regulator
PCM
Power Conditioning Module
PDM
Power Distribution Module
MPPT
Maximum Power Point Tracker
USB
Universal Serial Bus
ESD
Electro Static Discharge
TLM
Telemetry
EPS
Electrical Power System
EoC
End of Charge
AMUX
Analogue Multiplexer
ADC
Analogue to Digital Converter
AIT
Assembly, Integration and Testing
1U
1 Unit (Cubesat standard size)
3U
3 Unit (Cubesat standard size)
FleXU/XU
FleXible Unit (suitable for various satellite configurations)
rh
Relative Humidity
Wh
Watt Hour
Ah
Ampere Hour
DoD
-1
Kbits
Depth of Discharge
Kilobits per second
Voc
Open Circuit Voltage
Isc
Short Circuit Current
2s1p
Battery configuration – 2 cells in series, 1 battery in parallel (single string)
2s2p
Battery configuration – 2 cells in series, 2 batteries in parallel
2s3p
Battery configuration – 2 cells in series, 3 batteries in parallel
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 3 of 47
Related Documents
No.
Document Name
Doc Ref.
RD-1
Battery board User Manual
TBC
RD-2
CubeSat Design Specification
CubeSat Design Specification Rev. 12
RD-3
NASA General Environmental
Verification Standard
GSFC-STD-7000 April 2005
RD-4
CubeSat Kit Manual
UM-3
RD-5
Solar Panel User Document
Power System Design and
Performance on the World’s Most
Advanced In-Orbit Nanosatellite
TBC
RD-6
#
As named
Risk
Warning
1
Ensure headers H1 and H2 are correctly aligned
before mating boards
If misaligned, battery positive can short to
ground, causing failure of the battery and EPS
2
Ensure switching configuration is implemented
correctly before applying power to EPS
If power is applied with incorrect switch
configuration, the output of the BCR can be
blown, causing failure of the EPS and subsequent
damage to the battery
3
Observe ESD precautions at all times
The battery is a static sensitive system. Failure
to observe ESD precautions can result in failure
of the battery
4
Ensure not to exceed the maximum stated limits
Exceeding any of the stated maximum limits can
result in failure of the battery
5
Ensure batteries are fully isolated during storage
If not fully isolated (by switch configuration or
separation) the battery may over-discharge,
resulting in failure of the battery
6
No connection should be made to H2.35-36
These pins are used to connect the battery to
the EPS. Any connections to the unregulated
battery bus should be made to pins H2.43-44
7
H1 and H2 pins should not be shorted at any
time
These headers have exposed live pins which
should not be shorted at any time. Particular
care should be taken regarding the surfaces
these are placed on.
8
Battery should only
integrated with an EPS
The EPS includes a number of protection circuits
for the battery.
Operation without these
protections may lead to damage of the batteries
9
Do not discharge batteries below 6V
If the battery is discharged to a voltage below 6V
the cells have been compromised and will no
longer hold capacity
If batteries are over-discharged DO NOT attempt
to recharge
If the battery is over discharged (below 6V) it
should not be recharged as this may lead to cell
rupture.
10
10
be
operated
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© Clyde Space Limited 2010
USM-0007
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Issue: B
1.
Date: 25/09/2014
Page: 4 of 47
Helix Building, WSSP,
Glasgow G20 0SP, UK
Introduction .......................................................................................................................... 6
1.1
Additional Information Available Online ............................................................................................6
1.2
Continuous Improvement ...................................................................................................................6
1.3
Document Revisions ...........................................................................................................................6
2.
Overview ............................................................................................................................... 7
3.
Maximum Ratings .............................................................................................................. 8
4.
Electrical Characteristics ....................................................................................................... 9
5.
Handling and storage .......................................................................................................... 10
(1)
5.1
Electro Static Discharge (ESD) Protection .........................................................................................10
5.2
General Handling ..............................................................................................................................10
5.3
Shipping and Storage ........................................................................................................................10
6.
Materials and Processes ..................................................................................................... 11
6.1
Materials Used ..................................................................................................................................11
6.2
Processes and Procedures ................................................................................................................11
7.
System Description ............................................................................................................. 12
7.1
System Overview ..............................................................................................................................14
7.2
Autonomy and Redundancy .............................................................................................................15
7.3
Quiescent Power Consumption ........................................................................................................15
7.4
Mass and Mechanical Configuration ................................................................................................15
8.
Interfacing........................................................................................................................... 16
8.1
Connector Layout .............................................................................................................................17
8.2
Solar Array Connection .....................................................................................................................18
8.3
Solar Array Harness ..........................................................................................................................20
8.4
Temperature sensing interface .........................................................................................................20
8.5
Non-Clyde Space Solar Arrays ...........................................................................................................20
8.6
CubeSat Kit Compatible Headers ......................................................................................................21
8.7
Cubesat Kit Header Pin Out ..............................................................................................................22
8.8
Switch Options ..................................................................................................................................24
8.9
Battery connection ...........................................................................................................................26
8.10
Buses.................................................................................................................................................27
9.
Technical description .......................................................................................................... 28
9.1
Charge Method .................................................................................................................................28
9.2
BCR Power Stage Overview ..............................................................................................................29
9.3
MPPT ................................................................................................................................................29
9.4
5V and 3.3V PCM ..............................................................................................................................30
10.
General protection ............................................................................................................. 31
10.1
Over-Current Bus Protection ............................................................................................................31
10.2
Battery Under-voltage Protection ....................................................................................................32
11.
11.1
Telemetry and Telecommand ............................................................................................. 33
2
I C Node ............................................................................................................................................33
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Page: 5 of 47
Helix Building, WSSP,
Glasgow G20 0SP, UK
11.2
I²C Command Interface.....................................................................................................................33
11.3
Command Summary .........................................................................................................................35
11.4
ADC Channels ...................................................................................................................................37
12.
Test ..................................................................................................................................... 39
12.1
Power up/Down Procedure ..............................................................................................................39
12.2
Solar Array Input ...............................................................................................................................40
12.3
Battery Setup ....................................................................................................................................41
12.4
Configuration and Testing ................................................................................................................41
13.
Developer AIT ..................................................................................................................... 45
14.
Compatible Systems ........................................................................................................... 47
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Page: 6 of 47
Helix Building, WSSP,
Glasgow G20 0SP, UK
1. INTRODUCTION
This document provides information on the features, operation, handling and storage of
the Clyde Space 3U EPS. The 3U EPS is designed to integrate with a suitable battery and
solar arrays to form a complete power system for use on a 3U CubeSat.
Figure 1-1 System Diagram
1.1 Additional Information Available Online
Additional information on CubeSats and Clyde Space Systems can be found at
www.clyde-space.com. You will need to login to our website to access certain
documents.
1.2 Continuous Improvement
At Clyde Space we are continuously improving our processes and products. We aim to
provide full visibility of the changes and updates that we make, and information of these
changes can be found by logging in to our website: www.clyde-space.com.
1.3 Document Revisions
In addition to hardware and software updates, we also update make regular updates to
our documentation and online information. Notes of updates to documents can also be
found at www.clyde-space.com.
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Page: 7 of 47
Helix Building, WSSP,
Glasgow G20 0SP, UK
2. OVERVIEW
This is the second generation of Clyde Space CubeSat Electronic Power System,
developed by our team of highly experienced Spacecraft Power Systems and Electronics
Engineers.
Since introducing the first generation in 2006, Clyde Space has shipped over 120 EPS to
customers in Europe, Asia and North America. The second generation EPS builds on the
heritage gained with the first, whilst adding over 50% additional power delivery
capability. Furthermore, we have also implemented an ideal diode mechanism, to
ensure zero draw on the battery in launch configuration.
Clyde Space is the World leading supplier of power system components for CubeSats.
We have been designing, manufacturing, testing and supplying batteries, power system
electronics and solar panels for space programmes since 2006. Our customers range
from universities running student led missions, to major space companies and
government organisations.
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© Clyde Space Limited 2010
USM-0007
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Issue: B
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 8 of 47
3. MAXIMUM RATINGS(1)
OVER OPERATING TEMPERATURE RANGE (UNLESS OTHERWISE STATED)
4
Input Voltage
(2)
BCR
Value
Unit
SA1 (pin 1 or pin 4)
BCR1 (8W)
25
V
SA2 (pin 1 or pin 4)
BCR2 (8W)
25
V
SA3 (pin 1 or pin 4)
BCR3 (3W)
10
V
Battery
8.3
V
5V Bus
5.05
V
3.3V Bus
3.33
V
Value
Unit
BCR1
@16V
750
mA
BCR2
@16V
750
mA
BCR3
@6V
750
mA
Battery Bus
@8.26V
6
A
5V Bus
@5V
4
A
3.3V Bus
@3.3V
4
A
Operating Temperature
-40 to 85
°C
Storage Temperature
-50 to 100
°C
Input Current
Output Current
-5
Vacuum
10
torr
Radiation Tolerance
(TBC)
kRad
Shock
(TBC)
Vibration
To [RD-3]
Table 3-1 Max Ratings of the 3U EPS
(1)
Stresses beyond those listed under maximum ratings may cause permanent damage to the EPS. These are the
stress ratings only. Operation of the EPS at conditions beyond those indicated is not recommended. Exposure
to absolute maximum ratings for extended periods may affect EPS reliability
(2)
De-rating of power critical components is in accordance with ECSS guidelines.
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© Clyde Space Limited 2010
USM-0007
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Issue: B
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 9 of 47
4. ELECTRICAL CHARACTERISTICS
Description
Conditions
Min
Typical
Max
Unit
Input Voltage
10
--
25
V
Output Voltage
6.2
--
8.26
V
Output Current
0
--
1.2
A
245
250
255
KHz
85%
90%
92%
Input Voltage
3.5
--
8
V
Output Voltage
6.2
--
8.26
V
Output Current
0
--
0.5
A
160
170
180
KHz
77%
79%
80%
Output Voltage
6.2
--
8.26
V
Output Current
--
4
4.2
A
Operating Frequency
--
--
--
98.5%
99%
99.5%
Output Voltage
4.95
5
5.05
V
Output Current
--
2.5
2.9
A
470
480
490
kHz
95%
96%
98%
Output Voltage
3.276
3.3
3.333
V
Output Current
--
2.5
2.9
A
Operating Frequency
470
480
490
kHz
94%
95%
97%
Protocol
--
IC
--
Transmission speed
--
100
400
Bus voltage
3.26V
3.3V
3.33V
Node address
--
0x2B
--
Address scheme
--
7bit
--
Node operating frequency
--
8MHz
--
8W BCR (1&2)
Switching Frequency
Efficiency
@16.5V input, Full Load
3W BCR (3)
Operating Frequency
Efficiency
@6V input, Full Load
Unregulated Battery Bus
Efficiency
@8.26V input, Full Load
5V Bus
Operating Frequency
Efficiency
@5V input, Full Load
3.3V Bus
Efficiency
@3.3V input, Full Load
Communications
2
-1
Kbits
Hex
Quiescent Operation
Power Draw
Flight
Configuration
Switches
of
Physical
Dimensions
Height from top of PCB to
bottom of next PCB in stack
Weight
--
--
<0.1
L
W
H
W
95
90
15.24
mm
80
83
86
g
Table 4-1 Performance Characteristics of the 3U EPS
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Page: 10 of 47
Helix Building, WSSP,
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5. HANDLING AND STORAGE
The EPS requires specific guidelines to be observed for handling, transportation and
storage. These are stated below. Failure to follow these guidelines may result in
damage to the units or degradation in performance.
5.1 Electro Static Discharge (ESD) Protection
3
The EPS incorporates static sensitive devices and care should be taken during handling.
Do not touch the EPS without proper electrostatic protection in place. All work carried
out on the system should be done in a static dissipative environment.
5.2 General Handling
The EPS is robust and designed to withstand flight conditions. However, care must be
taken when handling the device. Do not drop the device as this can damage the EPS.
There are live connections between the battery systems and the EPS on the CubeSat Kit
headers. All metal objects (including probes) should be kept clear of these headers.
Gloves should be worn when handling all flight hardware.
Flight hardware should only be removed from packaging in a class 100000 (or better)
clean room environment.
5.3 Shipping and Storage
The devices are shipped in anti-static, vacuum-sealed packaging, enclosed in a hard
protective case. This case should be used for storage. All hardware should be stored in
anti-static containers at temperatures between 20°C and 40°C and in a humiditycontrolled environment of 40-60%rh.
The shelf-life of this product is estimated at 5 years when stored appropriately.
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© Clyde Space Limited 2010
USM-0007
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Issue: B
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 11 of 47
6. MATERIALS AND PROCESSES
6.1 Materials Used
Material
Manufacturer
%TML
%CVCM
%WVR
Application
1.
Araldite 2014 Epoxy
Huntsman
0.97
0.05
0.33
Adhesive fixing
2.
1B31 Acrylic
Humiseal
3.89
0.11
0.09
Conformal
Coating
3.
DC 6-1104
Dow Corning
0.17
0.02
0.06
Adhesive fixing
on modifications
4.
Stycast 4952
Emerson &
Cuming
0.42
0.17
0.01
Thermally
Conductive RTV
5.
PCB material
FR4
0.62
0
0.1
Note: worst case
on NASA outgassing list
6.
Solder Resist
CARAPACE
EMP110 or
XV501T-4
0.95
or 0.995
0.02
Or 0.001
0.31
-
7.
Solder
Sn62 or Sn63
(Tin/Lead)
-
-
-
-
8.
Flux
Alpha Rosin
Flux, RF800, ROL
0
-
-
-
Low activity flux
to avoid
corrosion
Table 6-1 Materials List
Part Used
Manufacturer
Contact
Insulator
Type
Use
DF13-6P-1.25DSA(50)
Hirose
Gold Plated
Polyamide
PTH
Solar Array
Connectors
ESQ-126-39-G-D
Samtec
Gold Plated
Black Glass Filled
Polyester
PTH
CubeSat Kit
Compatible
Headers
DF13-6S-1.25C
Hirose
N/A
Polyamide
Crimp Housing
Harness for Solar
Arrays (sold
separately)
DF13-2630SCFA(04)
Hirose
Gold Plated
N/A
Crimp
Harness for Solar
Arrays (sold
separately)
Table 6-2 Connector Headers
6.2 Processes and Procedures
All assembly is inspected to ESA Workmanship Standards; ECSS-Q-ST-70-08C and ECSSQ-ST-70-38C.
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Page: 12 of 47
Helix Building, WSSP,
Glasgow G20 0SP, UK
7. SYSTEM DESCRIPTION
The Clyde Space 3U EPS is optimised for Low Earth Orbit (LEO) missions with a maximum
altitude of 850km. The EPS is designed for integration with spacecraft that have six or
less body mounted solar panels (i.e. one on each spacecraft facet). The EPS can
accommodate various solar panel configurations, and has been designed to be versatile;
please consult our support team if you have specific requirements for connecting the
EPS to your spacecraft.
The Clyde Space EPS connects to the solar panels via three independent Battery Charge
Regulators (BCRs). These are connected as shown in Figure 7-1 and Figure 7-2 with
panels on opposing faces of the satellite connected to the same BCR (e.g. –X array and
+X array are connected to BCR1, -Y and +Y to BCR2 and –Z and +Z to BCR3). In this
configuration only one panel per pair can be directly illuminated at any given time, with
the second panel providing a limited amount of energy due to albedo illumination. Each
of the BCRs has an inbuilt Maximum Power Point Tracker (MPPT). This MPPT will track
the dominant panel of the connected pair (the directly illuminated panel).
The output of the three BCRs are then connected together and, via the switch network,
(described in Section 7.2), supply charge to the battery, Power Conditioning Modules
(PCMs) and Power Distribution Modules (PDMs) via the switch network.
The PCM/PDM network has an unregulated Battery Voltage Bus, a regulated 5V supply
and a regulated 3.3V supply available on the satellite bus. The EPS also has multiple
inbuilt protection methods to ensure safe operation during the mission and a full range
of EPS telemetry via the I2C network. These are discussed in detail in Sections 10 and
Error! Reference source not found. respectively.
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© Clyde Space Limited 2010
USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 13 of 47
+Z Array
-Y Array
-X Array
+X Array
+Y Array
-Z Array
Figure 7-1 Array Configuration
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USM-0007
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Issue: B
7.1
Date: 25/09/2014
Helix Building, WSSP,
Glasgow G20 0SP, UK
Page: 14 of 47
System Overview
H1.43
I2C CLOCK
H1.41
I2C DATA
TLM
conditioning
AMUX
H2.35-36
PCM_IN
I2C Node
CTRL
3.3V PCM
CTRL
5V PCM
BUCK
CTRL
BUCK
CTRL
SHDN
TLM
O/C
CIRCUIT
TLM
SHDN
TLM
Vbatt
Current
sensing
O/C
CIRCUIT
H2.45-46
BATTERY BUS
CTRL
H2.27-28
+3.3V BUS
H2.25-26
+5V BUS
CTRL
I2C BUFFER
UNDER
VOLTAGE
CTRL
PCM / PDM network
T
L
M
H2.29,31-32
GND
END OF
CHARGE
3W SEPIC BCR
BCR3
8W BUCK BCR
TLM
-ARRAY
TLM
5
6
TLM
TLM
1
2
3
4
I
I
V
+ARRAY
-ARRAY
TLM
TLM
TLM
SENSING
TLM
1
2
3
4
+ARRAY
+ARRAY
5
-ARRAY 6
V
TLM
I
I
TLM
V
SENSING
TLM
I
I
1
2
3
4
TLM
5
6
SENSING
BCR/
MPPT
BCR/
MPPT
BCR/
MPPT
BCR2
8W BUCK BCR
BCR1
H2.41-44
BCR_OUT
IDEAL
DIODE
H1.32
5v USB
Figure 7-2 Function Diagram
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Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
Page: 15 of 47
Helix Building, WSSP,
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7.2 Autonomy and Redundancy
All BCR power stages feature full system autonomy, operating solely from the solar array
input and not requiring any power from the battery systems. This feature offers inbuilt
redundancy as the failure of one BCR does not affect remaining BCRs. Failure of the all
strings of the battery (any of the CS-SBAT2-xx range) will not damage the BCRs but, due
to the MPPT, will result in an intermittent interruption on all power buses
(approximately every 2.5 seconds). Failure of one battery on the CS-SBAT-20 or two
batteries on the CS-SBAT2-30 will not damage the BCRs and the system can continue to
operate with a reduced capacity of 10Wh.
The rest of the power system is a robustly designed single string.
7.3 Quiescent Power Consumption
All power system efficiencies detailed (for BCRs and PCMs) takes into consideration the
associated low level control electronics. As such, these numbers are not included in the
quiescent power consumption figures.
The I2C node is the only circuitry not covered in the efficiency figures, and has a
quiescent power consumption of ≈0.1W, which is the figure for the complete EPS.
7.4 Mass and Mechanical Configuration
The mass of the system is approximately 83g and is contained on a single PC/104 size
card, compatible with the Cubesat Kit bus. Other versions of the EPS are available
without the Cubesat Kit bus header.
Figure 7-3 Mechanical Diagram
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Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
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Helix Building, WSSP,
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8. INTERFACING
The interfacing of the EPS is outlined in
Figure 8-1, including the solar array inputs, connection to the switch configuration,
output of the power buses and communication to the I2C node. In the following section
it is assumed that the EPS will be integrated with a Clyde Space Battery (CS-SBAT210/20/30).
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USM-0007
Issue: B
User Manual: 25-00221 - 2x8W Buck, 1x3W SEPIC
EPS 2G (3U)
Date: 25/09/2014
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Helix Building, WSSP,
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Figure 8-1 Clyde Space EPS and Battery Simplified Connection Diagram
8.1 Connector Layout
1
The connector positions are shown in Figure 7-3, and described in Table 8.1.
Connector
Function
SA1
Solar Array connector for 8W +/- arrays
SA2
Solar Array connector for 8W +/- arrays
SA3
Solar Array connector for 3W +/- arrays
H1
Cubesat Kit bus compatible Header 1
H2
Cubesat Kit bus compatible Header 2
Table 8-1 Connector functions
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8.2 Solar Array Connection
The EPS has three connectors for the attachment of solar arrays. This interface
accommodates inputs from the arrays with temperature telemetry for each.
Figure 8-2 Example Solar Array Configuration
HIROSE DF13-6P-1.25 DSA connector sockets are used on the EPS. These are labelled
SA1-SA3. SA1-SA2 are routed to BCR1-BCR2 respectively. These BCRs are capable of
interfacing to 8W panels and should be harnessed to arrays with between 6-8 triple
junction solar cells in series.
SA3 routes to BCR3, which is a 3W channel that should be harnessed to the small arrays.
The array lengths should be the same on joined panels, with 2 cells each.
Figure 8-3 Solar Array Pin Numbering
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Name
Use
Notes
1
+ YARRAY (8W)
+ Power Line
Power
2
GND
Ground Line
Power RTN and GND connection
for Temp Sensor
3
+YARRAY_TEMP_TELEM
+ YArray Telemetry
Telemetry
4
- YARRAY (8W)
- Power Line
Power
5
GND
Ground Line
Power RTN and GND connection
for Temp Sensor
6
-YARRAY_TEMP_TELEM
- YArray Telemetry
Telemetry
Table 8-2 Pin out for Header SA1
Pin
Name
Use
Notes
1
+ XARRAY(8W)
+ Power Line
Power
2
GND
Ground Line
Power RTN and GND connection
for Temp Sensor
3
+XARRAY_TEMP_TELEM
+ XARRAY Telemetry
Telemetry
4
- XARRAY (8W)
- Power Line
Power
5
GND
Ground Line
Power RTN and GND connection
for Temp Sensor
6
-XARRAY_TEMP_TELEM
- ARRAY Telemetry
Telemetry
Table 8-3 Pin out for Header SA2
Pin
Name
Use
Notes
1
+ ZARRAY (3W)
+ Power Line
Power
2
GND
Ground Line
Power RTN and GND connection
for Temp Sensor
3
+ZARRAY_TEMP_TELEM
+ ZARRAY Telemetry
Telemetry
4
- ZARRAY (8W)
- Power Line
Power
5
GND
Ground Line
Power RTN and GND connection
for Temp Sensor
6
-ZARRAY_TEMP_TELEM
- ZARRAY Telemetry
Telemetry
Table 8-4 Pin out for Header SA3
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8.3 Solar Array Harness
Clyde Space supply harnesses (sold separately) to connect the solar panels to the EPS,
comprising two Hirose DF13-6S-1.25C connected at each end of the cable; one end
connects to the EPS, with two halves of the harness connecting to opposing solar panels.
Clyde Space solar arrays use Hirose DF13-6P-1.25H as the interface connector to the
harness.
8.4 Temperature sensing interface
Temperature sensing telemetry is provided for each solar array connected to the EPS. A
compatible temperature sensor (LM335M) is fitted as standard on Clyde Space solar
arrays (for non-Clyde Space panels refer to section 8.5). The output from the LM335M
sensor is then passed to the telemetry system via on board signal conditioning. Due to
the nature of the signal conditioning, the system is only compatible with zener based
temperature sensors i.e. LM335M or equivalent. Thermistor or thermocouple type
sensors are incompatible with the conditioning circuit.
Figure 8-4 Temperature sensor block diagram
8.5 Non-Clyde Space Solar Arrays
When connecting non-Clyde Space solar arrays care must be taken with the polarity,
Pins 1,2 and 3 are for array(+)and pins 4, 5 and 6 relate to the opposite array (-). Cells
used should be of triple junction type. If other cells are to be interfaced please contact
Clyde Space.
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Page: 21 of 47
8.6 CubeSat Kit Compatible Headers
1
Connections from the EPS to the bus of the satellite are made via the CubeSat Kit
compatible headers H1 and H2, as shown in Figure 8-5.
6
7
H1
H2
5V BUS
5V BUS
3.3V BUS
3.3V BUS
GND
GND
USB 5V
R265
NF
R264
NF
BATT POS
BATT POS
PCM IN
PCM IN
DUMMY LOAD
DUMMY LOAD
N/C
N/C
I2C
DATA
R255
NF
BCR OUT
BCR OUT
I2C CLK
BAT BUS
BAT BUS
Figure 8-5 CubeSat Kit Header Schematic
3.3V BUS
5V BUS
BATT
GND POS
USB
CHARGING
PCM IN
BCR OUT
BAT BUS
DUMMY LOAD I2C DATA I2C CLK
Figure 8-6 EPS Connector Pin Identification
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8.7 Cubesat Kit Header Pin Out
HEADER 1
Use
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
21
ALT I C
CLK
Alt I2C clock connection
22
NC
Not Connected
HEADER 2
Use
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Notes
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
NC
Not Connected
Not Connected
22
NC
Not Connected
Not Connected
23
NC
Not Connected
Not Connected
24
25
26
NC
+5V BUS
+5V BUS
+3.3V
BUS
+3.3V
BUS
Not Connected
+5V Power bus
+5V Power bus
+3V3 Power
bus
+3V3 Power
bus
Ground
connection
Ground
connection
Not Connected
Ground
connection
Not Connected
Regulated 5V bus
Regulated 5V bus
23
ALT I C
DATA
Alt I C data connection
24
25
26
NC
NC
NC
Not Connected
Not Connected
Not Connected
Notes
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
0ohm resistor
R265 (must fit to
operate)
Not Connected
0ohm resistor
R264 (must fit to
operate)
Not Connected
Not Connected
Not Connected
27
NC
Not Connected
Not Connected
27
28
NC
Not Connected
Not Connected
28
29
NC
Not Connected
Not Connected
29
GND
30
NC
Not Connected
Not Connected
30
GND
31
NC
Not Connected
31
NC
32
USB_5
USB 5+v
Not Connected
Use to charge
battery via USB
2
2
2
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Name
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
21
32
GND
BATT
POS
BATT
POS
33
NC
Not Connected
Not Connected
33
34
NC
Not Connected
Not Connected
34
35
NC
Not Connected
Not Connected
35
PCM IN
36
NC
Not Connected
Not Connected
36
PCM IN
Power line
Power line
Power line
Power line
37
NC
Not Connected
Not Connected
37
38
NC
Not Connected
Not Connected
38
DL
39
40
NC
NC
Not Connected
Not Connected
39
40
NC
NC
41
I2C DATA
I2C data
Not Connected
Not Connected
Data for I2C
communications
Dummy Load
Protection
Dummy Load
Protection
Not Connected
Not Connected
41
BCR OUT
Power line
NC
Not Connected
Not Connected
42
BCR OUT
Power line
43
BCR OUT
Power line
44
BCR OUT
Power line
42
43
I C CLK
I C clock
Clock for I2C
communications
44
NC
Not Connected
Not Connected
2
2
45
NC
Not Connected
Not Connected
45
46
NC
Not Connected
Not Connected
46
47
48
49
NC
NC
NC
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
47
48
49
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DL
Battery
Bus
Battery
Bus
NC
NC
NC
+Bat Power Bus
+Bat Power Bus
Not Connected
Not Connected
Not Connected
Regulated 3V3 bus
Regulated 3V3 bus
System power
return
System power
return
Not Connected
System power
return
Pull pin normally
connected pin
Pull pin normally
connected pin
Sep SW normally
connected pin
Sep SW normally
connected pin
Pull pin normally
open pin
Pull pin normally
open pin
Not Connected
Not Connected
Common point PP
+SS pins
Common point PP
+SS pins
Common point PP
+SS pins
Common point PP
+SS pins
Output to battery
bus
Output to battery
bus
Not Connected
Not Connected
Not Connected
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50
51
52
Name
NC
NC
NC
Date: 25/09/2014
HEADER 1
Use
Not Connected
Not Connected
Not Connected
Notes
Not Connected
Not Connected
Not Connected
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Page: 23 of 47
Pin
50
51
52
Name
NC
NC
NC
HEADER 2
Use
Notes
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Not Connected
Table 8-5 Pin Descriptions for Header H1 and H2
6
NODE
HEADER
CUBESAT KIT NAME
NOTES
+5V BUS
2.25-26
+5V
5V Regulated Bus Output
+3.3V BUS
2.27-28
VCC_SYS
3.3V Regulated Bus Output
BATT POS
2.33-34
SW0
Positive Terminal of Battery (not Battery Bus)
DO NOT CONNECT
PCM IN
2.35-36
SW1
(Switches )
Input to PCMs and PDMs
DUMMY LOAD
2.37-38
SW2
(Switches )
N/C
2.39-40
SW3
(Switches N/C)
Unused connection of launch switch closed state
BCR OUT
2.41-44
SW4
Output of BCRs
( Switches)
BCR OUT
2.41-44
SW5
Output of BCRs
( Switches)
BATTERY BUS
2.45-46
VBATT+
Battery Unregulated Bus Output
Table 8-6 Header pin name descriptions relating CubeSat Kit names to CS names
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8.8 Switch Options
The Clyde Space EPS has three connection points for switch attachments, as shown in
Figure 8-7. There are a number of possible switch configurations for implementation.
Each configuration must ensure the buses are isolated from the arrays and battery
during launch. The batteries should also be isolated from the BCRs during launch in
order to conform to CubeSat standard [RD-2].
Figure 8-7 Switch connection points
Dummy Load
The Dummy Load is available as an additional ground support protection system,
providing a load for the BCRs when the pull pin is inserted using the normally open (NO)
connection of the Pull Pin. By connecting this Dummy Load to the NO pin BCR damage
can be circumvented. The wiring arrangement for the dummy load is indicated in Figure
8-8.
The load protects the battery charge regulator from damage when the USB or array
power is attached and the batteries are not connected. This system is not operational
during flight and is only included as a ground support protection.
The Clyde Space Dummy Load system has been a standard feature on all revisions of the
EPS2. If the Dummy Load is required for an earlier revision please contact Clyde Space
for fitting instructions.
Options 1 and 2 below are two suggested methods of switch configuration, but are by
no means exhaustive. If you wish to discuss other possible configurations please contact
Clyde Space.
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Option 1
Figure 8-8 Switch Configuration Option 1
Option 1 accommodates the CubeSat Kit bus available switches offering two-stage
isolation. The separation switch provides isolation of the power buses during the launch.
The pull pin may be used for ground based isolation of the batteries, though it does not
provide any isolation during launch.
NOTE: The second generation Clyde Space EPS has zero-current draw when the pull pin
is removed – i.e. there will be no current drawn from the battery while on the launch
vehicle.
When pull pin is inserted, the battery is isolated from the output of the BCRs. Under
these conditions, if power is applied to the input of the arrays, or by connecting the USB,
there is a possibility of damaging the system. In order to mitigate this risk a “Dummy
Load” is fitted on the EPS.
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Option 2
Figure 8-9 Switch Configuration Option 2
Option 2 is compatible with structures incorporating two separation switches, providing
complete isolation in the launch configuration. The dummy load is not activated in this
configuration.
Care should be taken to ensure that the switches used are rated to the appropriate
current levels.
Please contact Clyde Space for information on implementing alternative switch or
dummy load configurations.
8.9 Battery connection
1
4
Connection of the battery systems on the 3U EPS is via the Cubesat kit bus. Ensure that
the pins are aligned, and located in the correct position, as any offset can cause the
battery to be shorted to ground, leading to catastrophic failure of the battery and
damage to the EPS. Failure to observe these precautions will result in the voiding of any
warranty.
When the battery is connected to the EPS, the battery will be fully isolated until
implementing and connecting a switch configuration, as discussed in Section 8.8. Ensure
that the battery is fully isolated during periods of extended storage.
When a battery board is connected to the CubeSat Kit header, there are live,
unprotected battery pins accessible (H2.33-34). These pins should not be routed to any
connections other than the switches and Clyde Space EPS, otherwise all protections will
be bypassed and significant battery damage can be sustained.
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Buses
All power buses are accessible via the CubeSat Kit headers and are listed and described
in Table 8-5. These are the only power connections that should be used by the platform
since they follow all battery and bus over-current protections.
All I2C communications can are accessible via the CubeSat kit header. See Section 11.
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9. TECHNICAL DESCRIPTION
This section gives a complete overview of the operational modes of the EPS. It is
assumed that a complete Clyde Space system (EPS, Batteries and Solar panels) is in
operation for the following sections.
9.1 Charge Method
The BCR charging system has two modes of operation: Maximum Power Point Tracking
(MPPT) mode and End of Charge (EoC) mode. These modes are governed by the state of
charge of the battery.
MPPT Mode
If the battery voltage is below the preset EoC voltage the system is in MPPT mode. This
is based on constant current charge method, operating at the maximum power point of
the solar panel for maximum power transfer.
EoC Mode
Once the EoC voltage has been reached, the BCR changes to EoC mode, which is a
constant voltage charging regime. The EoC voltage is held constant and a tapering
current from the panels is supplied to top up the battery until at full capacity. In EoC
mode the MPPT circuitry moves the solar array operation point away from the
maximum power point of the array, drawing only the required power from the panels.
The excess power is left on the arrays as heat, which is transferred to the structure via
the array’s thermal dissipation methods incorporated in the panels.
The operation of these two modes can be seen in Figure 9-1.
end of charge voltage
Figure 9-1 Tapered charging method
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The application of constant current/constant voltage charge method on a spacecraft is
described in more detail in RD-6. In this document there is on-orbit data showing the
operation and how the current fluctuates with changing illumination conditions and
orientation of the spacecraft with respect to the Sun.
9.2 BCR Power Stage Overview
As discussed in Section 8, the EPS has three separate, independent BCRs, each designed
to interface to two parallel solar arrays on opposing faces of the satellite. Two 8W BCRs
interface to the panels in the X and Y axes, and a third, smaller, 3W BCR interfaces to the
panel on the Z axis.
Each design offers a highly reliable system that can deliver 90% (8W BCR) or 80% (3W
BCR) of the power delivered from the solar array network at full load.
8W BCR power stage
The 8W BCR is a BUCK converter, allowing the BCR to interface to strings of six to eight
cells in series. This will deliver up to 90% output at full load. The design will operate
with input voltages between 10V and 24V and a maximum output of 8.26V (7.4V
nominal).
3W BCR Power Stage Design
Each 3W BCR uses a high efficiency SEPIC converter, interfacing to solar arrays of two
triple junction cells in series. This will deliver up to 80% output at full load. The BCR will
operate with an input of between 3V and 6V and a maximum output of 8.26V (7.4V
nominal).
9.3 MPPT
Each of the BCRs can have two solar arrays connected at any given time; only one array
can be illuminated by sunlight, although the other may receive illumination by albedo
reflection from earth. The dominant array is in sunlight and this will operate the MPPT
for that BCR string. The MPPT monitors the power supplied from the solar array. This
data is used to calculate the maximum power point of the array. The system tracks this
point by periodically adjusting the BCRs to maintain the maximum power derived from
the arrays. This technique ensures that the solar arrays can deliver much greater usable
power, increasing the overall system performance.
Increasing
Temperature
Maximum Power Point
Is/c
Array Current
I MPP
Increasing
Temperature
V MPP
V o/c
Array Voltage
Figure 9-2 Solar Array Maximum Power Point
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The monitoring of the MPP is done approximately every 2.5 seconds. During this
tracking, the input of the array will step to o/c voltage, as shown in Figure 9.3.
Figure 9-3 Input waveform with Maximum Power Point Tracking
9.4 5V and 3.3V PCM
The 5V and 3.3V regulators both use buck switching topology regulators as their main
converter stage. The regulator incorporates intelligent feedback systems to ensure the
voltage regulation is maintained to +/- 1% deviation. The efficiency of each unit at full
load is approximately 96% for the 5V PCM and 95% for the 3.3V PCM. Full load on each
of the regulator have a nominal output current of 2.5A (which is upgradable to 4.5A).
Each regulator operates at a frequency of 480 kHz.
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10. GENERAL PROTECTION
The EPS has a number of inbuilt protections and safety features designed to maintain
safe operation of the EPS, battery and all subsystems supplied by the EPS buses.
10.1
Over-Current Bus Protection
The EPS features bus protection systems to safeguard the battery, EPS and attached
satellite sub-systems. This is achieved using current monitors and a shut down network
within the PDMs.
Over-current shutdowns are present on all buses for sub system protection. These are
solid state switches that monitor the current and shutdown at predetermined load
levels, see Table 10-1. The bus protection will then monitor the fault periodically and
reset when the fault clears. The fault detection and clear is illustrated in the waveform
in Figure 10-1.
SYSTEM
SHUTDOWN
OVER CURRENT
EVENT
TEST PERIOD
EVENT
CLEARS
TEST
PERIOD
SYSTEM
RESUME
BUS VOLTAGE
CURRENT
NORMAL
LEVEL
NORMAL
OPERATION
NORMAL
OPERATION
Shutdown period
Shutdown period
Shutdown period
Figure 10-1 Current protection system diagram
Bus
Battery Bus
5V Bus
3.3V Bus
Period
Approximate Duration (ms)
Shutdown period
Test period
650
60
Shutdown period
Test period
585
30
Shutdown period
525
Test period
30
Table 10-1 Bus protection data
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Battery Under-voltage Protection
In order to prevent the over-discharge of the battery the EPS has in-built under-voltage
shutdown. This is controlled by a comparator circuit with hysteresis. In the event of the
battery discharging to ~6.2V (slightly above the 6.1V that results in significant battery
degradation) the EPS will shutdown the supply buses. This will also result in the I2C node
shutting down. When a power source is applied to the EPS (e.g. an illuminated solar
panel) the battery will begin charging immediately. The buses, however, will not
reactivate until the battery voltage has risen to ~7V. This allows the battery to charge to
a level capable of sustaining the power lines once a load is applied.
It is recommended that the battery state of charge is monitored and loading adjusted
appropriately (turning off of non critical systems) when the battery capacity is
approaching the lower limit. This will prevent the hard shutdown provided by the EPS.
Once the under-voltage protection is activated there is a monitoring circuit used to
monitor the voltage of the battery. This will draw approximately 2mA for the duration
of shutdown. As the EPS is designed for LEO orbit the maximum expected period in
under-voltage is estimated to be ~40mins. When ground testing this should be taken
into consideration, and the battery should be recharged within 40mins of reaching
under-voltage, otherwise permanent damage may be sustained.
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11. TELEMETRY AND TELECOMMAND
The telemetry system monitors certain stages of the power system and allows a small
degree of control over the PDM stages. The telemetry system transfers data via an I2C
bus. The telemetry system operates in slave mode and requires an I2C master to supply
commands and the clock signal. Control systems within the EPS offer the user the ability
to temporarily isolate the EPS buses from the on-board computer systems.
ARRAY Sense
voltage
BCR1 Sense
current
ARRAY Sense
voltage
temperture
BCR2 Sense
current
ARRAY Sense
voltage
temperture
BCR3 Sense
current
AMUX
temperture
I2C data bus
I2C NODE
Sensing
Current
VBAT
PDM
Sensing
Current
5V PDM
Sensing
Current
3.3V
PDM
Signal line
Control line
Figure 11-1 Telemetry functional diagram
11.1
I2C Node
The I2C Node is based on the Microchip PIC16F690. The device node is configured to act
as a single channel analogue to digital converter. The microcontroller controls the
analogue multiplexer that routes the signals from the sensors. The PIC16F690 program is
designed to operate as a slave sensor node on the I2C bus. The program will select and
then convert the desired signal data from the telemetry network on demand. There is
also a control feature that can briefly shutdown PDMs within the EPS.
The following sections briefly describe the hardware that is used.
Analogue Multiplexer
A 32 channel analogue multiplexer is used for selecting the correct sensor signal. The
multiplexer is controlled from the microcontroller.
Additional Hardware
Further required hardware includes an oscillator and an I2C bus extender. The oscillator
provides a robust clock signal for the microcontroller. The bus extender provides greater
robustness to signal noise on the I²C bus during integration and operations.
11.2
I²C Command Interface
All communications to the Telemetry and Telecommand, TTC, Node are via an I²C
interface. The TTC Node is configured as a slave and only responds to direct commands
from a master I²C node. No unsolicited telemetry is transmitted. A maximum 400Kbit
bus speed is supported, with typical bus speeds of 100Kbit. The address of the TTC Node
is factory set. The address is 0x2B.
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Message Formats
Two message structures are available to the master; a write command and a read
command. The write command is used to initiate an event and the read command
returns the result. All commands start with the 7 bit slave address and are followed by
two data bytes. The first data byte should be the command. The second byte represents
the data that is used as part of the command. An example of the data is the analogue to
digital channel to read.
An example of a read command would be:

The master transmits the slave address with write flag, command type (0x00)
and data (ADC channel)

The slave acts on the commands, sets the correct channel and reads the
analogue to digital converter

The master transmits the slave address with read flag

The slave responds with a two-byte value
If a read message does not have a preceding write message, the value 0xF000 is
returned. All bit level communication to and from the board is done by sending the MSB
first. If both bytes are not read then the system may become unstable.
ADC
The I2C node acts as a multi channel Analogue to digital convertor which allows the
board to supply sensor data to the user. When the command is received, a delay,
approximately 1.2ms, is inserted to allow the analogue reading to settle. After this delay
the result can be retrieved. The result is a 10 bit value with the first byte received
containing the two most significant bits and the second byte received the remaining 8
bits.
MSB
LSB
First byte
Second byte
Used bits
Figure 11-2 ADC 10bit data packet
To retrieve a sensor reading the following procedure should be used:
Send 0x00 followed by 0x0X, where X represents the channel number in Hex format.
This instructs the I2C node that the user wishes to retrieve a sensor value and which
sensor to take the reading from.
After a small delay, approximately 1.2ms, the user can issue a read command and the
result will be transmitted. The most significant byte is sent first followed by the least
significant byte.
The result received should then be entered into the conversion equations, covered in a
further section, which calculates the requested parameter.
If the reading is not yet ready 0xF000 is returned
This process should be followed for all ADC channels.
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Command Summary
Table 11-1, below, provides a list of the commands for the EPS. The data that should
accompany the commands is included in the table. Descriptions of the commands follow
the table.
Command Type
Command
Value Range
Description
Decimal
Name
Decimal
0
ADC
0-31
Read ADC Channel
1
Status
N/A
Request Status Bytes
2
PDM Off
0-7
Turns off the selected PDM for a short time
4
Version
N/A
Request Firmware Version
128
Watchdog
N/A
Causes a soft reset of the micro
Table 11-1 Command Summary
Status
The status bytes are designed to supply operational data about the I2C Node. To retrieve
the two bytes that represent the status the command 0x01 should be sent. The meaning
of each bit of the status byte is shown in Table 11-2.
PDM Off
There may be a time when the user wishes to turn of the PDM’s for a short period. They
may wish to do this to create a hard reset of a circuit. To carry this out the command
0x0002 is sent followed by the data byte. The data byte has a range of 0 to 7. Bit 0
corresponds to the battery bus, bit 1 the 5V bus and bit 2 the 3.3V bus. Any combination
of busses can be turned off, however is should be noted that if the user switches the
3.3V PDM off the I2C node will be reset.
Version
The firmware version number can be accessed by the user using this command. Please
contact Clyde Space to learn the version number on your board.
WatchDog
The Watchdog command allows the user to force a reset of the I2C node. If the user
detects or suspects an error in the operation of the I2C node then this command should
be issued. When issued the I2C node will reset and return to an initial state.
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Bit
Description
If Low (0)
If High (1)
Note
0
Unknown Command Type
Last command OK
Last Command
Unknown
Bit cleared
when read
1
Unknown Command Value
Last Command Value OK
Last Command
Value Out of
Range
Bit cleared
when read
2
ADC Result Not Ready
ADC Result Ready
ADC Result Not
Ready
Bit cleared
when read
3
Not Used
-
-
Reads as ‘0’
4
Oscillator bit
External
running
External
Oscillator failure
-
5
Watchdog Reset Occurred
No Watchdog Reset
Watchdog Reset
Occurred
Bit cleared
when read
6
Power On Reset Occurred
Power
On
Occurred
Reset
No Power On
Reset Occurred
Bit cleared
when read
7
Brown Out Reset Occurred
Brown
Out
Occurred
Reset
No Brown Out
Reset Occurred
Bit cleared
when read
0
I C Error
I2C
Occurred
Error
Bit cleared
when read
I C Write Collision
I2C
Collision
Occurred
Write
1
2
Oscillator
2
No I C Errors
2
No I C Write Collision
I C Overflow
2
No I C Overflow
IC
Overflow
Occurred
3
Received Message to Long
Received
Messages
Correct Length
Last
Message
incorrect Length
4-7
Not Used
-
-
1
2
2
2
-
2
-
Reads as ‘0’
Table 11-2 Status Bytes
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ADC Channels
Each of the analogue channels, when read, returns a number between 0-1023. To
retrieve the value of the analogue signal this number, ADC, is to be entered into an
equation. When the equation is used the value calculated is the value of the input
analogue signal. Table 11-4 contains example equations of the conversions of each of
the channels. To get more accurate equations full calibration test should be carried out.
ADC
Channel
Signal
0
GND
1
+Y Array Current
2
+Y Array
Temperature
3
Array Pair Y
Voltage
4
-Y Array Current
5
-Y Array
Temperature
6
Array Pair X
Voltage
7
-X Array Current
8
-X Array
Temperature
9
Array Pair Z
Voltage
10
+Z Array Current
11
+Z Array
Temperature
12
GND
13
+X Array Current
14
+X Array
Temperature
15
GND
-
-
16
GND
-
-
17
Battery Bus
Current
18
GND
-
-
19
GND
-
-
20
GND
-
-
Approx Conversion Equations
Units
-
-
-2.7153
x
2146.464646
ADC
Count
+
-0.163 x ADC count + 110.338
mA
°C
-0.021668284 x ADC Count +
25.06218798
V
-2.7153
x
2146.464646
mA
ADC
Count
+
-0.163 x ADC count + 110.338
°C
-0.021668284 x ADC Count +
25.06218798
V
-2.7153
x
2146.464646
mA
ADC
Count
+
-0.163 x ADC count + 110.338
°C
-0.021668284 x ADC Count +
25.06218798
V
-2.7153
x
2146.464646
mA
ADC
Count
+
-0.163 x ADC count + 110.338
°C
-
-
-2.7153
x
2146.464646
ADC
Count
+
-0.163 x ADC count + 110.338
-6.788313
5366.1616
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x
ADC
Count
mA
°C
+
mA
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21
GND
-
-
22
GND
-
-
23
GND
-
-
24
GND
-
-
25
GND
-
-
26
5V Bus Current
-6.788313
5366.1616
x
ADC
Count
+
27
3.3V Bus Current
-6.788313
5366.1616
x
ADC
Count
+
28
GND
-
-
29
GND
-
-
30
-Z Array
Temperature
31
-Z Array Current
-0.163 x ADC count + 110.338
-2.7153
x
2146.464646
ADC
Count
mA
mA
°C
+
mA
Table 11-3 ADC Channels
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12. TEST
All EPS are fully tested prior to shipping, and test reports are supplied. In order to verify
the operation of the EPS please use the following outlined instructions.
Step by step intro of how to connect and verify operation:
In order to test the functionality of the EPS you will require:







Battery (or simulated battery)
Breakout Connector (with connections as per Figure 12-1)
Array Input (test panel, solar array simulator or power supply and limiting
resistor)
Oscilloscope
Multimeter
Electronic Load
Aardvark I2C connector (or other means of communicating on the I2C bus)
Figure 12-1 Suggested Test Setup
The breakout connector should be wired with the switch configuration to be used under
mission conditions.
12.1
Power up/Down Procedure
The order of assembly should follow the order detailed below:







Breakout connector assembled with switches set to launch vehicle configuration
(as shown in Figure 12-1)
Fit Breakout connector to EPS
Connect battery to stack
Connect electronic load (no load) to buses
Remove Pull Pin
Activate Separation Switch
Connect array input
When powering down this process should be followed in reverse.
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Solar Array Input
There are 3 options for the array input section:



A solar array
A solar array simulator
A benchtop power supply with current limiting resistor
When using a solar array or solar array simulator the limits should not exceed those
outlined in Table 12-1
Voc (V)
Isc (mA)
BCR1
24.5
464
BCR2
24.5
464
BCR3
6.13
464
Table 12-1 solar array limits
When using a power supply and resistor setup to simulate a solar panel the required
setup is shown in Figure 12-2.
Figure 12-2 Solar Panel using power supply
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Battery Setup
The system should be tested with a battery in the system. This can be done using a
Clyde Space Battery by stacking the boards, or by using a power supply and load to
simulate the behavior of a battery. This setup is shown in Figure 12-3.
Figure 12-3 Simulated Battery Setup
12.4
Configuration and Testing
The following section outlines the procedure for performing basic functional testing
PCM Testing
In order to test the PCMs power must be applied to the PCM_IN connection. In order to
do this the “Pull Pin” should be removed, connection the battery, as shown in Figure 124.
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Figure 12-4 Test set-up with Pull Pin Removed
In this configuration all buses will be activated and can be measured with a multimeter.
By increasing the load on each of the buses you will be able to see the current trip
points' activation, as discussed in Section 10.1.
Undervoltage Protection
When using a simulated battery it is possible to trigger the undervoltage protection.
Using the same test setup as detailed above, with a simulated battery if the voltage is
dropped to below ~6.2V the undervoltage will be activated. This can be observed by the
power buses shutting down.
4
Note: This test takes the battery to 100% DoD and should always be followed by a
charge cycle.
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BCR Testing
In order to test the operation of the BCRs the separation switches should be moved to
flight configuration, as shown in Figure 12-5, (with the pull pin still removed). Once this
is done the array input can be connected.
Figure 12-5 Test set-up in Flight Configuration
To check the operation of the BCR/MPPT an oscilloscope probe should be placed at pin 1
of the active solar array connector (not at the power supply). The wave form should
resemble Figure 12-6.
Figure 12-6 Waveform of Solar Array Input
EoC Operation
Using the test setup detailed in Figure 12-5 the EoC operation can be demonstrated. By
raising the voltage of the simulated battery above ~8.26V the EoC mode will be
activated. This can be observed using an ammeter coming from the Array input, which
will decrease towards 0A (it will never actually reach 0A, closer to 10mA as the BCR low
level electronics will still draw form the array).
5V USB Charging
Figure 12-7 shows the test setup for the 5V USB charging.
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Figure 12-7 Waveform of Solar Array Input
This setup should only be used for top up charge on the battery, not for mission
simulation testing.
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13. DEVELOPER AIT
AIT of the EPS with other CubeSat modules or subsystems is the responsibility of the
CubeSat developer. Whilst Clyde Space outlines a generic process which could be
applicable to your particular system in this section we are not able to offer more specific
advice unless integration is between other Clyde Space products (or those of compatible
products), see Table 14-1. AIT is at the risk of the developer and particular care must be
taken that all subsystems are cross-compatible.
Throughout the AIT process it is recommended that comprehensive records of all
actions be maintained tracking each subsystem specifically. Photo or video detailing of
any procedure also helps to document this process. Comprehensive records are useful
to both the developer and Clyde Space; in the event of any anomalies complete and
rapid resolution will only be possible if good records are kept. The record should
contain at least;

Subsystem and activity

Dates and times of activity (start, finish, key milestones)

Operator(s) and QAs

Calibration of any equipment

Other subsystems involved

Method followed

Success condition or results

Any anomalous behaviour
Before integration each module or element should undergo an acceptance or preintegration review to ensure that the developer is satisfied that the subsystem meets its
specification through analysis, inspection, review, testing, or otherwise. Activities might
include:

Satisfactory inspection and functional test of the subsystem

Review of all supporting documentation

Review of all AIT procedural plans, identifying equipment and personnel needs
and outlining clear pass/fail criteria

Dry runs of the procedures in the plan
Obviously testing and analysis is not possible for all aspects of a subsystem specification,
and Clyde Space is able to provide data on operations which have been performed on
the system, as detailed in Table 13-1.
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Performed on
Availability
Functional
Module supplied
Provided with module
Calibration
Module supplied
Provided with module
Vacuum
Performed on module prototype
In manual
Thermal
Performed on module prototype
In manual
Simulation & modelling
Not performed
Not available
Table 13-1 Acceptance test data
Following this review, it is recommended the system undergoes further testing for
verification against the developer’s own requirements. Commonly requirement
compliance is presented in a compliance matrix, as shown in Table 13-2.
ID
Requirement
Procedure
Result (X)
Success criteria
Compliance
(pass / fail)
SYS-0030
The system mass
shall be no more
than 1 kg
TEST-01
0.957 kg
X < 1 kg
PASS
SYS-0040
The
error
LED
remains
off
at
initialisation
TEST-02
LED
flashing
LED off
FAIL
SYS-0050
…
…
…
…
…
Table 13-2 Compliance matrix example
All procedural plans carried out on the EPS should conform to the test setups and
procedures covered in Section 12.
During testing it is recommended that a buddy system is employed where one individual
acts as the quality assurance manager and one or more perform the actions, working
from a documented and reviewed test procedure. The operator(s) should clearly
announce each action and wait for confirmation from their QA. This simple practice
provides a useful first check and helps to eliminate common errors or mistakes which
could catastrophically damage the subsystem.
Verification is project dependant, but should typically start with lower-level subsystemspecific requirements which can be verified before subsystems are integrated; in
particular attention should be paid to the subsystem interfaces to ensure crosscompatibility.
Verification should work upwards towards confirming top-level
requirements as the system integration continues. This could be achieved by selecting a
base subsystem (such as the EPS, OBC or payload) and progressively integrating modules
into a stack before structural integration. Dependent upon the specific systems and
qualification requirements further system-level tests can be undertaken.
When a subsystem or system is not being operated upon it should be stowed in a
suitable container, as per Section 5.
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14. COMPATIBLE SYSTEMS
Stacking
Connector
Compatibility
Notes
CubeSat Kit Bus
CubeSat Kit definition pin compatible
Non-standard Wire Connector
User defined
Other Connectors
Please contact Clyde Space
Clyde Space Battery Systems
10W/hr – 30 W/hr Lithium Ion Polymer
CS-SBAT2-10/-20/-30
CS-RBAT2-10
Lithium Polymer 8.2v
(2s1p) to (2s3p)
(1)
More strings can be connected in parallel
to increase capacity if required
Batteries
Lithium Ion 8.2v
(2s1p) to (2s3p)
(1)
More strings can be connected in parallel
to increase capacity if required
Solar Arrays
Structure
Other Batteries
Please contact Clyde Space
Clyde Space 3W solar array
Connects to BCR 3 via SA3
Clyde Space 8W solar array
Connects to BCR 1/2 via SA1/2
3W triple junction cell arrays
2 in series connection
8W triple junction cell arrays
6-8 in series connection
Other array technologies
Any that conform to the input ratings for
(2)
Voltage and Current
Pumpkin
CubeSat 3U structure
ISIS
CubeSat 3U compatible
Other structures
Please contact Clyde Space
Table 14-1 Compatibilities
(1) Refers to series and parallel connections of the battery cells within the battery system.
e.g. 2s1p indicates a single string of two cells in series.
(2) Will require some alteration to MPPT. Please contact Clyde Space.
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